Field of the Invention
The present invention relates generally to the field of biopotential signal analysis, e.g., detecting, monitoring and/or processing electrocardiogram (ECG), electroencephalogram (EEG) or electromyography (EMG) signals. More specifically the invention relates to a system and a method for the analysis of such biopotential signals using motion artifact removal techniques.
Description of the Related Art
In real life situations and ambulatory recordings of biopotential signals, motion artifacts result from relative movement of recording electrodes, cables, and acquisition system with respect to the skin and the environment. The most significant changes during motion are happening on the interface between the skin and the electrodes. These might be due to changes in the charge distribution along the contact surface or skin deformations and hence changes in conduction within the skin. However, different type of movements might induce distinct changes in the measured electrical activity.
A known system that proposes motion artifact removal from ECG signals is described in “Motion Artifact Removal using Cascade Adaptive Filtering for Ambulatory ECG Monitoring System”, Hyejung Kim et al., IEEE Proceedings of Biomedical Circuits and Systems (BioCAS), 2012.
Another known technique for motion artifact removal from ECG signals is disclosed in “Implementation of Fuzzy-rule based Activity Classification and Optimized Adaptive Filter-set for Wearable ECG Recording”, Yun-Hong Noh and Do-Un Jeong, International Journal of Multimedia and Ubiquitous Engineering, Vol. 7, No. 4, October 2012. The solution proposes the use of an adaptive filter with an optimal filter coefficient selection to remove motion artifacts. With the data obtained from a three-axis accelerometer, activity status can be classified into different states and optimal filter coefficients can then be selected to minimize the distortion of ECG signal.
U.S. Pat. No. 5,513,649 describes an EEG (electroencephalogram) system that detects brain waves from a subject, and reduces the adverse effect of artifacts due to head, body and eye movements. A head and body movement reference signal can be provided by an accelerometer, motion detector or, alternatively, spatial average of EEG channels. Eye motion sensors are used as a reference for eye movement artifacts.